A tunnel boring machine (TBM) is designed for different geological conditions. Typically, a TBM is fitted with a number of cutting head tools, such as, ripper tools for softer rock conditions, for example. Ripper tools experience abrasive wear as well as impact loading. A ripper tool is considered a wear part that may be replaced repeatedly during the excavation of a given tunnel. It can be costly and time consuming to replace these ripper tools. As such, the industry highly values ripper tools possessing superior wear life.
A conventional ripper tool is manufactured by attaching carbide inserts to steel shanks through brazing. It has been observed that the brazing process softens the material of the shank, making it more susceptible to abrasive wear and other failures. In operation, this softened steel has a tendency to become “washed away” during cutting operations by abrasive action such that the shanks of the carbide inserts become exposed. The loss of the material allows the inserts to break off before the inserts themselves are completely worn, thereby necessitating the premature replacement of a ripper tool that otherwise still would have cutting life remaining.
U.S. Pat. No. 6,339,868 is entitled, “Cutting Tool and Shrink Fitting Method for the Same.” The '868 patent is directed to a cutting tool including a tool holding portion and a tool. The tool is configured to be inserted into a hole of the tool holding portion. The tool includes a tool main body, a guide portion, and a shoulder portion. The tool main body has a tool outer diameter that is larger than the inner diameter of the hole when the tool holding portion is not heated. The guide portion is coaxially connected to the tool main body and configured to position the tool substantially coaxially with respect to the tool holding portion. The guide portion has a guide outer diameter that is smaller than the inner diameter of the hole so that the guide portion can be inserted into the hole. The shoulder portion is formed between the tool main body and the guide portion so as to sit on a surface around the hole to support the tool when the guide portion is inserted into the hole.
The '868 patent is also directed to a cutting tool shrink fitting method which includes inserting a guide portion which is coaxially connected to a tool main body of a tool into a hole formed in a tool holding portion in order to support and position the tool substantially coaxially with respect to the tool holding portion such that a shoulder portion which connects the tool main body and the guide portion sits on a surface around the hole of the tool holding portion. The tool holding portion is heated such that the tool main body of the tool can be inserted into the hole. The tool holding portion is cooled.
It will be appreciated that this background description has been created by the inventor to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some aspects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.